nixos-rebuild

TLDR

Build and switch to the new configuration, making it the boot default

$ sudo nixos-rebuild switch

Build and switch to the new configuration, making it the boot default and naming the boot entry

$ sudo nixos-rebuild switch -p [name]

Build and switch to the new configuration, making it the boot default and installing updates

$ sudo nixos-rebuild switch --upgrade

Rollback changes to the configuration, switching to the previous generation

$ sudo nixos-rebuild switch --rollback

Build the new configuration and make it the boot default without switching to it

$ sudo nixos-rebuild boot

Build and activate the new configuration, but don't make a boot entry (for testing purposes)

$ sudo nixos-rebuild test

Build the configuration and open it in a virtual machine

$ sudo nixos-rebuild build-vm